1. Field of the Invention
The present invention relates generally to a vibration motor installed in a mobile terminal as call incoming means together with a bell, and more particularly, to a vibration motor which is fixed through the press fit by a shaft thereby enabling the axis with precise erectness while eliminating malfunctions due to a mechanical assembly error.
2. Description of the Prior Art
In general, one of essential functions in communication instruments is a call incoming function, which is mostly provided in a sound mode such as melody or bell and a vibration mode vibrating a communication instrument.
In other words, when a user previously selected a call incoming function, the selected function is operated at the time of call incoming so that the user can notice the call incoming.
In such call incoming modes, in particular, the vibration mode is generally used in a place where a number of people are gathered so as not to interrupt others.
In the sound mode such as melody or bell of the call incoming function, a number of melody or bell types are previously stored in the instrument to be outwardly transmitted through a small sized speaker allowing the user to notice the call incoming. In the vibration mode, generally a small sized vibration motor is operated to transfer a vibration force to a housing of the instrument so that the instrument can be vibrated.
Meanwhile, the vibration mode of the prior art is obtained by using a vibration motor installed in the instrument. As shown in FIG. 1 and FIG. 2, one of the most typical vibration motors, so-called xe2x80x9cpan cakexe2x80x9d or xe2x80x9ccoin typexe2x80x9d motor, has the outer shape with the diameter relatively larger than the thickness.
Such a vibration motor has a plate-type cover plate 100 in the bottom. The cover plate 100 has a tubular burring part 100a in the center. The tubular burring part 100a has an axial hole in the center projected at a certain height so that the lower end of a shaft 140 can be fixedly press fit into the axial hole. Also, in the upper surface of the cover plate 100 is a lower board 110 with a printed circuit which enables external power application.
At the upper surface of the cover plate 100 having the lower board 110 like this are arranged magnets 130 in the annular shape having a vertical through-hole defined in the center of the magnets 130 and N and S poles arranged alternately with the equal gap at the round periphery thereof.
The lower board 110 in the bottom of a central space of the magnets 130 is spaced from a pair of brushes 120 with one ends respectively connected to input and output ends of the magnets 130 and the other ends positioned higher than the upper surfaces of the magnets 130.
Meanwhile, a cylindrical housing 150 is coupled with the cover plate 100 the end of outer periphery thereof to cover the cover plate 100. The housing 150 has a shaft hole 150a in the upper center for receiving the shaft 140 while supporting the same.
In this manner, the shaft 140, the lower board 110, the magnets 130 and the pair of brushes 120 supported by the cover plate 100 define a stator. In respect to the stator is rotationally arranged an eccentric rotor 200 comprising an upper board 210, commutators 220 and winding coils 240.
Here, the upper board 210 is a typical printed circuit board which is made of a plate-type member cut at an arbitrary angle, and supported by the shaft 140 and a bearing b so that the upper board 210 can be eccentrically rotated. Such an upper board 210, in the bottom opposed to the cover plate 100, is integrally provided with the commutators 220 comprising a number of segments. The segments of the commutators 220 contact with the upper ends of a pair of brushes 120 with the lower ends connected to the lower board 110.
The winding coils 240 are attached to the upper surface of the upper board 210 without a printed circuit, and are composed of at least one coil according to an operation mode of the vibration motor. In particular, when the winding coils 240 are made of the plurality of coils, the coils are spaced at a predetermined angle from one another.
Also, the upper board 210, in the surface without the winding coil 240, is integrally provided with an insulator 250 for enhancing insulation and eccentric load between the winding coils 240 in the upper board 210. The insulator 250 is integrally formed through insert extrusion together with the commutators 220 and the winding coils 240 attached to the upper board 210 when the upper board 210 is made. The adjacent pair of winding coils 240 have a weight 230 made of a heavy metal such as tungsten in order to maximize the eccentric amount.
Meanwhile, the shaft 140 is in the peripheries of the upper and lower ends coupled into discal upper and lower washers w1 and w2 with through holes in the center thereof. When the eccentric rotor 200 is elevated or dropped in the operation of the motor, the upper and lower washers w1 and w2 directly contact with the housing 150 and the cover plate 100 to prevent destruction.
In the conventional vibration motor having the foregoing configuration, when an electric power is externally applied through the lower board 110, the electric power is induced to the commutators 220 through the brushes 120 with the lower ends connected to the lower board 110 and then supplied to the winding coils 240 through the printed circuit on the upper board 210 from the commutators 220 so that an electromagnetic force is generated from the interaction between magnetic fluxes from the winding coils 240 and the magnets 130 to rotate the eccentric rotor 200.
Here, the eccentric rotor 200 is eccentrically supported by the shaft 140 to exert an eccentric driving force, which is transferred to the cover plate 100 and the housing 150 through the shaft 140 to drive silent call-incoming means of a mobile communication terminal.
However, in the vibration motor of the prior art, while the lower end thereof is fixedly press fit into the cover plate 100, the upper end of the shaft 140 is simply inserted into the shaft hole 150a of the housing 150 so that the erectness of the shaft is unstable resultantly lowering the performance of the motor as a problem.
In other words, the shaft hole 150a has the inside diameter larger in respect to the outside diameter of the shaft to assemble the shaft 140 into the shaft hole 150a of the housing 150 so that a play, even if slight, is created between the shaft 140 and the shaft hole 150a when the shaft 140 is assembled into the shaft hole 150a. Therefore, the upper end of the shaft 140 is played within the shaft hole 150a due to side pressure to incur damage and noise according to inter-component contact in the operation of the motor. In particular, as the erectness of the shaft 140 becomes unstable, the operation features of the eccentric rotor 200 is also degraded causing problems such as reduced life time.
Accordingly, the present invention has been proposed to solve the foregoing problems and it is an object of the present invention to provide a vibration motor which can ensure the erectness of a shaft more precise while stably fixing one end of the shaft into a housing through press fit so that operation features and endurance can be enhanced.
It is another object of the present invention to enable absorptive damping of the impact in the operation of the eccentric motor to stably maintain the operation features of the motor.
According to an embodiment of the invention to obtain the foregoing object, it is provided a vibration motor comprising: a cover plate for fixedly receiving the lower end of a shaft in a central part; a housing coupled with the cover plate to define a certain size of space and having a recess in an upper inner central part; a lower board attached to the upper surface of the cover plate and having brushes projected at one end; magnets attached to the upper surface of the cover plate; an upper board rotationally supported while being eccentric by the shaft and having commutators made of a number of segments in the bottom for electric connection with the brushes; a plurality of winding coils distanced from each other at an angle in the upper surface of the upper board; an insulator made of a resin for fixing the plurality of winding coils to the upper board; and support means made of an elastic material, the support means being attached while covering the recess of the housing and having incisions for being spread toward the recess to center the shaft when the upper end of the shaft is press fit into a central part of the incisions.
Preferably, the incisions of the support means are radially incised about the center.
Also preferably, the incisions of the support means is sized smaller than the outside diameter of the shaft.
Preferably also, the incisions of the support means have the center coinciding with that of the shaft.
Also preferably, the support means has an adhesive coated with a height on the outer periphery of the incisions opposed to the recess of the housing.
According to another embodiment of the invention to obtain the foregoing object, it is provided a vibration motor comprising: a cover plate having a tubular burring part provided in an upper central part for fixedly receiving the lower end of a shaft; a housing coupled with the cover plate to define a certain size of space and having a recess in an upper inner central part; a lower board attached to the upper surface of the cover plate and having brushes projected at one end; magnets attached to the upper surface of the cover plate at the outside of the lower board; an upper board rotationally supported while being eccentric by the shaft and having commutators made of a number of segments in the bottom for electric connection with the brushes; a plurality of winding coils distanced from each other at an angle in the upper surface of the upper board; an insulator made of a resin for fixing the plurality of winding coils to the upper board; an upper washer made of an elastic material, the upper washer being attached while covering the recess of the housing and having incisions for being spread toward the recess when the upper end of the shaft is press fit into a central part of the incisions; and a lower washer coupled with the outer periphery of the shaft over the burring part.
Preferably, the incisions of the upper washer are radially incised about the center.
Also preferably, the incisions of the upper washer is sized smaller than the outside diameter of the shaft.
Preferably also, the incisions of the upper washer have the center coinciding with that of the shaft.
Also preferably, the upper washer has an adhesive coated with a height on the outer periphery of the incisions opposed to the recess of the housing.